This invention relates to a friction clutch driven plates and particularly, but not exclusively, to driven plates which are utilised in the friction clutches of automobiles.
A problem associated with some automobiles is that during the periods when the transmission drive is under no load, rotary oscillations occur in the gearbox producing a phenomenon known as idle-rattle.
In order to damp out the vibrations which generrate idle-rattle it is known to utilise a friction clutch driven plate in which the torque load through the driven plate passes through two sets of damping springs arranged in series with each other. Very light loads applied to the driven plate are taken through soft auxiliary vibration damping springing. When the limited angular movement controlled by the auxiliary damping springing has been taken up, normal drive load passes through a set of main torsion damping springs. In this way, very soft springing is provided over a limited range of movement for very light loads and this arrangement tends to prevent idle-rattle. Such a driven plate is known from French Patent Publication No. 1501465.
It is often important for a friction clutch driven plate to be compact in order to enable it to fit within a space available in an existing design of drive line or to assist in maintaining the combination of engine, clutch and gearbox as short as possible in a completely new design.
It is also known, for example from UK published patent application 2 087 043 A to use a circumferentially extending spring arm as the spring medium for the auxiliary friction damping. This kind of arrangement can be compact in an axial direction. However it is necessary for the auxiliary springing to be sufficiently powerful to overcome friction inherent in the clutch driven plate so that the auxiliary springing operates effectively. The spring force available from a circumferentially acting spring, which must remain effective for the life of the clutch driven plate, may be insufficient for practical requirements.
An object of the present invention is to provide a compact design of clutch driven plate having main torsion damping springing and effective auxiliary torsion damping springing.